Writing in The National today, he said independent Ireland in 1922 used the pound successfully for a prolonged period without being in a currency union with the UK before moving to its own currency. The policy was also managed despite the country having to deal with years of civil war, he said.

His intervention comes ahead of the SNP’s conference where currency proposals based on Andrew Wilson’s Growth Commission are to be debated. The report recommended continuing to use the pound – outwith a currency union with the UK – until six economic tests are met before moving towards the introduction of a new currency.

However, some in the party’s grassroots demanded an independent Scotland should have its own currency to ensure greater control over economic policy. Derek Mackay and Keith Brown have put down a motion revising Wilson’s plan to give more guarantees over working towards a new currency.

The issue is important for the Yes movement as the policy in 2014 – to keep the pound but in a currency union with the UK – was seen as flawed when the UK said it would not take part in a currency union.

Hughes Hallet was a member of the Growth Commission and holds important academic and advisory roles. He is an honorary professor in economics at the University of St Andrews; professor of economics at Copenhagen BusinessSchool; professor emeritus, economics and public policy at George Mason University; Arlington, USA; senior research fellow at Kings College, University of London and adviser to the European Parliament on economic and monetary affairs.

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